(S)-pregabalin is an anticonvulsive drug which is also indicated in the treatment of generalised anxiety disorder (GAD) in adults, and the treatment of peripheral and central neuropathic pain in adults. Its chemical name is (3S)-3-(aminomethyl)-5-methylhexanoic acid or (S)-(+)-4-amino-3-(2-methylpropyl)butanoic acid, and it has the following chemical structure:

A synthesis of (S)-pregabalin is described by Hayashi et al. (Organic Letters, 2007, Vol. 9, No. 25, 5307-5309). The synthesis comprises conjugate addition of nitromethane to α,β-unsaturated aldehydes in the presence of a diphenylprolinol silyl ether catalyst to give an aliphatic nitro compound which undergoes oxidation followed by reduction to (S)-pregabalin (Scheme 1).

The catalyst is prepared in six steps. The scale up of the synthesis is difficult making it unsuitable for use on an industrial scale.
The present invention provides an efficient method for preparing gamma amino acids such as (S)-pregabalin, preferably in high enantiomeric purity.